1. Field of the Invention
The present invention relates to improvements in a rotary compressor that is available as a refrigerant compressor for use in refrigeration or air-conditioning or the like, and more particularly to reduction of noise in such rotary compressor.
2. Description of the Prior Art
At first, description will be made of a rotary compressor in the prior art, by way of example, in connection with a refrigerant compressor for use in refrigeration or air-conditioning, with reference to FIGS. 9 to 15. In these figures, reference numeral 1 designates a tightly closed housing, and at the top of this housing is provided a delivery pipe 2 for leading compressed refrigerant gas within the housing to the outside. To this delivery pipe 2 are successively connected a condenser 4, a throttling mechanism 5, an evaporator 6 and an accumulator 7 via refrigerant pipings 3, and the accumulator 7 is communicated with a cylinder chamber 20 within the tightly closed housing 1 via a suction pipe 8. Reference numeral 9 designates an inlet portion of the suction pipe 8 within the accumulator 7. A gaseous refrigerant sucked from the inlet portion 9 through the suction pipe 8 into the cylinder chamber 20 is compressed, then it is delivered into a delivery cavity 13 through a delivery port 34 and a delivery valve 42, and thereafter it is led out to a space portion 14 within the tightly closed housing 1, passed around a motor 11 and delivered to the outside of the tightly closed housing 1 through the delivery pipe 2.
Reference numeral 12 designates a crank shaft and numeral 15 designates lubricating oil kept at the bottom of the tightly closed housing. Reference numeral 30 designates a cylinder main body fixedly secured to the lower portion of the tightly closed housing 1. At the upper and lower ends of the cylinder main body 30 are fixedly secured by bolts an upper bearing 40 and a lower bearing 41, respectively, which rotatably support the crank shaft 12, and thereby the tightly closed cylinder camber 20 is formed. Within the cylinder chamber 20 is disposed a rotor 31 loosely fitted on an eccentric portion of the crank shaft 12, and this cylinder chamber 20 is partitioned into a suction side space 20a communicating with the suction pipe 8 and a compression side space 20b by means of a partition plate 32 which is slidably fitted in a groove provided in the cylinder main body 30 so that the tip end of the partition plate 32 on the side of the cylinder chamber 20 may be pressed against the outer circumferential surface of the rotor 31.
The above-mentioned delivery port 34 is provided in the upper bearing 40 contiguously to the partition plate 32 so as to communicate with the compression side space 20b, and to this delivery port 34 is mounted delivery valve 42 via a retainer 43 and a bolt 44. Reference numeral 33 designates a notched groove provided in the cylinder 30 for the purpose of ensuring that a portion of a cross-sectional area of the passageway between the delivery port 34 and the cylinder chamber 20 is open, and compressed gas is adapted to be delivered from this notched groove 33 through the delivery port 34.
In the rotary compressor having the abovementioned construction, while refrigerant gas at a low pressure is being sucked through the suction pipe 8 into the suction side space 20a, the gas sucked during the preceding rotation is compressed in the compression side space 20b, the volume of which is being reduced as the rotor 31 rotates, and thereafter the gas is passed through the notched groove 33 and the delivery port 34 and delivered through the delivery valve 42. However, the notched groove 33 and the delivery port 34 form a so-called clearance volume, and the gas existing in this space portion will not be delivered through the delivery valve 42. Rather, but after the rotor 31 has passed the top clearance volume portion, such gas will flow reversely into the suction side space 20a which is in a suction stroke. Accordingly, if the pressure within this cylinder chamber 20 is measured, it has the behavior as shown in FIG. 12. In FIG. 12, the rotational angle of the rotor is shown along the abscissa, while the pressure within the cylinder chamber is shown along the ordinate, and since the gas in the top clearance volume portion will abruptly flow in the reverse direction into the suction side space 20a at a low pressure, a pressure waveform measured in the suction side space 20a will contain pulsations having a high frequency component as shown at A. Therefore, there is a problem in the prior art that due to the influence of these pulsations, the level of noise of a compressor is large.
Hence, in order to prevent these pulsations having a high frequency component, improved structures were invented in the prior art such that a buffer 35 making use of a sound effect as shown in FIGS. 13 and 14 was provided at the top clearance volume portion, or that a removed portion 36, of about several hundred microns in depth was provided from the notched groove 33 up to the suction side space 20a so as to leak gas gradually for the purpose of preventing the gas in the top clearance volume from leaking abruptly to the suction side space 20a as shown in FIG. 15.
However, the structure shown in FIGS. 13 and 14 involved the problem that if a part of the lubricating oil sucked into the cylinder during operation should enter the buffer 35 and the volume of the buffer should be filled with the lubricating oil, a sufficient noise reduction effect could not be obtained. On the other hand, the structure shown in FIG. 15 involved the problem that deterioration of performance due to leakage of gas generated when the rotor 31 reached the portion 36 greater than that generated in the case where the portion 36 is not present, was observed, and also, depending upon operating pressure conditions the effect was reduced due to a constant cross-sectional area of the leakage path. Moreover, since the depth of portion 36 was several hundred microns, the structure was associated with difficulties in machining, and in order to maintain the effect for a wide range of operating pressure conditions it was necessary to decrease the depth of the portion 36 and to elongate the length thereof, but this quickened the timing of leakage and would increase deterioration of performance.
In essence, the heretofore known rotary compressors involved the problems that due to abrupt leakage of gas in a top clearance volume into a cylinder space at a low pressure, pulsations having a high frequency component were generated in the cylinder space and noise caused by these pulsations were produced. Even with improved structures proposed for resolving the abovementioned problem, the improvement was not sufficient, and such proposals still involved deterioration of a performance caused by leakage of gas or difficulties in machining.